Nasal Patient Tracking Device and Method of Using the Same

ABSTRACT

A patient tracking device for insertion into a body cavity includes a flexible conformable sensor housing having a sensor cavity therein. The housing conforms to the body cavity when inserted therein. A sensor is disposed within the housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application includes subject matter similar to that disclosed inconcurrently filed U.S. Patent Application Attorney Docket No.5074A-000217-US. The entire disclosure of the above application isincorporated

FIELD

The present disclosure relates to registration between a patient, andimage data and particularly to a system to track movement of a patientduring a procedure.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Image guided medical and surgical procedures utilize patient imagesobtained prior to or during a medical procedure to guide a physicianperforming the procedure. Recent advances in imaging technology,especially in imaging technologies that produce highly-detailed, two,three, and four dimensional images, such as computed tomography (CT),magnetic resonance imaging (MRI), fluoroscopic imaging (such as with aC-arm device), positron emission tomography (PET), and ultrasoundimaging (US) has increased the interest in image guided medicalprocedures.

Typical image guided navigation systems generally require dynamicreference frames to track the position of the patient should patientmovement occur during the assisted procedure. The dynamic referenceframe is generally affixed to the patient in an immovable fashion. Thedynamic reference frame may also be used as a fiducial marker and may,therefore, be attached to the patient during the acquisition ofpre-operative images. This enables the image space to be aligned withpatient space during the navigated procedure. For example, with relationto a cranial procedure, the dynamic reference frame can be attached tothe skull by a bone screw. For other procedures, the dynamic referenceframe may be fixed to other boney portions also with bone screws.Methods for affixing the dynamic reference frames to a patient can beinvasive or inaccurate due to movement. Bone affixed dynamic referenceframes require an incision that can often be more than two centimetersin length. Skin mobility can lead to undesirable movement when using anon-invasive dynamic reference frame attachment such as tape.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

In one aspect of the disclosure, a patient tracking device for insertioninto a body cavity includes a flexible conformable sensor housing havinga sensor cavity therein. The housing conforms to the body cavity wheninserted therein. A sensor is disposed within the housing.

In another aspect of the disclosure, a method includes determining abody cavity for receiving a flexible resilient sensor housing;determining a sensor housing corresponding the body cavity; insertingthe sensor housing having a sensor within a sensor cavity of the housinginto the body cavity; conforming the sensor housing to a shape of thebody cavity; collecting position data of the body cavity from thesensor; maintaining registration of an image space to a patient space inresponse to the position data; and displaying a navigated location.

In yet another aspect of the disclosure, a method of forming a patienttracking device includes forming a sensor cavity within a flexibleconformable housing sized to fit within a body cavity; inserting anelectromagnetic sensor within the sensor cavity; and retaining theelectromagnetic sensor within the sensor cavity.

In still another aspect of the disclosure, a patient tracking device forinsertion into an oral cavity includes a sensor housing comprising afirst surface shaped to correspond to a pallet within the oral cavity.At least a portion of the first surface affixes the sensor housing tothe oral cavity. An electromagnetic sensor is coupled to the sensorhousing.

In another aspect of the disclosure, a method includes determining ashape of a pallet of an oral cavity of a patient, forming a sensorhousing comprising a first surface based on the shape of the pallet,coupling an electromagnetic sensor to the sensor housing and affixingthe sensor housing within the oral cavity.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is an environmental view in an operating theatre that uses a DRF(endonasal or palatal patient tracker) of the present disclosure;

FIG. 2 is a front view of the endonasal dynamic tracking device of FIG.1;

FIG. 3A is a first example of a patient tracking device within a bodycavity;

FIG. 3B is a second example of a patient tracking device within a bodycavity;

FIG. 3C is a third example of a patient tracking device within a bodycavity;

FIG. 4A is a partially exploded view of the patient tracking device;

FIG. 4B is an assembled view of the patient tracking device;

FIG. 5 is a perspective view of a sensor for the patient trackingdevice;

FIG. 6A is one example of a housing 310;

FIG. 6B is an end view of the housing of FIG. 6A;

FIG. 6C is a side view of the housing having a cavity therein;

FIG. 6D is a cross-sectional view of a housing having a cavity that isonly partially filled with a sensor.

FIG. 7A is a side view of an electromagnetic sensor with a cable 172;

FIG. 7B is a block diagrammatic view of an wireless EM sensor;

FIG. 8A is a cross-sectional view of an EM sensor within a housing withan adhesive retainer;

FIG. 8B is a cross-sectional view of an EM sensor within a housing witha clip or fastener;

FIG. 8C is a second cross-sectional view of an EM sensor within ahousing with a clip or fastener;

FIG. 9A is a side view of the housing 310 having an RF EM sensor and theretainer being adhesive;

FIG. 9B is a side view of the housing 310 having an RF EM sensor and theretainer being a clip or fastener;

FIG. 9C is a second example of a side view of the housing 310 having anRF EM sensor and the retainer being a clip or fastener;

FIG. 10 is a flowchart of a method for forming the patient trackingdevice; and

FIG. 11 is a method for using the patient tracking device.

FIG. 12 is a cutaway front view of the patient having an oral sensorhousing.

FIG. 13 is a cutaway side view of the patient having an oral sensorhousing.

FIG. 14 is a top perspective view of the sensor housing.

FIG. 15 is a bottom view of the sensor housing.

FIG. 16 is a view of the sensor housing mounted within a palate of apatient.

FIG. 17 is a side view of the sensor housing with the sensor mountedthereto.

FIG. 18 is a view of a first alternate method for mounting a sensorhousing.

FIG. 19 is a cutaway view of a sensor housing having a sensor mountedtherein.

FIG. 20 is a side view of a sensor having a sensor over-molded therein.

FIG. 21 is a flowchart of a method for forming the sensor.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

The subject disclosure is directed to an exemplary embodiment of asurgical procedure on a subject, such as a human patient. It isunderstood, however, that the system and methods described herein aremerely exemplary and not intended to limit the scope of the claimsincluded herein. In various embodiments, it is understood, that thesystems and methods may be incorporated into and/or used on non-animateobjects. The systems may be used to, for example, to register coordinatesystems between two systems for use on manufacturing systems,maintenance systems, and the like. For example, automotive assembly mayuse one or more robotic systems including individual coordinate systemsthat may be registered together for coordinated or consorted actions.Accordingly, the exemplary illustration of a surgical procedure hereinis not intended to limit the scope of the appended claims.

FIG. 1 is a diagrammatic view illustrating an overview of a procedureroom or arena. In various embodiments, the procedure room may include asurgical suite having a navigation system 26 that can be used relativeto a patient or subject 30. The navigation system 26 can be used totrack the location of one or more tracking devices, tracking devices mayinclude an imaging system tracking device 62, and/or a tool trackingdevice 66. A tool 68 may be any appropriate tool such as a drill,forceps, catheter, speculum or other tool operated by a user 72. Thetool 68 may also include an implant, such as a stent, a spinal implantor orthopedic implant. It should further be noted that the navigationsystem 26 may be used to navigate any type of instrument, implant, stentor delivery system, including: guide wires, arthroscopic systems,orthopedic implants, spinal implants, deep brain stimulation (DBS)probes, etc. Moreover, the instruments may be used to navigate or mapany region of the body. The navigation system 26 and the variousinstruments may be used in any appropriate procedure, such as one thatis generally minimally invasive or an open procedure including cranialprocedures.

An imaging device 80 may be used to acquire pre-, intra-, orpost-operative or real-time image data of a subject, such as the subject30. It will be understood, however, that any appropriate subject can beimaged and any appropriate procedure may be performed relative to thesubject. In the example shown, the imaging device 80 comprises an O-arm®imaging device sold by Medtronic Navigation, Inc. having a place ofbusiness in Louisville, Colo., USA. The imaging device 80 may have agenerally annular gantry housing 82 in which an image capturing portionis moveably placed. The image capturing portion may include an x-raysource or emission portion and an x-ray receiving or image receivingportion located generally or as practically possible 180 degrees fromeach other and mounted on a rotor relative to a track or rail. The imagecapturing portion can be operable to rotate 360 degrees during imageacquisition. The image capturing portion may rotate around a centralpoint or axis, allowing image data of the subject 80 to be acquired frommultiple directions or in multiple planes. The imaging device 80 caninclude those disclosed in U.S. Pat. Nos. 7,188,998; 7,108,421;7,106,825; 7,001,045; and 6,940,941; all of which are incorporatedherein by reference, or any appropriate portions thereof. In oneexample, the imaging device 80 can utilize flat plate technology havinga 1,720 by 1,024 pixel viewing area.

The position of the imaging device 80, and/or portions therein such asthe image capturing portion, can be precisely known relative to anyother portion of the imaging device 80. The imaging device 80, accordingto various embodiments, can know and recall precise coordinates relativeto a fixed or selected coordinate system. This can allow the imagingsystem 80 to know its position relative to the patient 30 or otherreferences. In addition, as discussed herein, the precise knowledge ofthe position of the image capturing portion can be used in conjunctionwith a tracking system to determine the position of the image capturingportion and the image data relative to the tracked subject, such as thepatient 30.

The imaging device 80 can also be tracked with a tracking device 62. Theimage data defining an image space acquired of the patient 30 can,according to various embodiments, be inherently or automaticallyregistered relative to an object space. The object or patient space canbe the space defined by a patient 30 in the navigation system 26. Theautomatic registration can be achieved by including the tracking device62 on the imaging device 80 and/or the determinable precise location ofthe image capturing portion. According to various embodiments, asdiscussed herein, imageable portions, virtual fiducial points and otherfeatures can also be used to allow for registration, automatic orotherwise. It will be understood, however, that image data can beacquired of any subject which will define the patient or subject space.Patient space is an exemplary subject space. Registration allows for atranslation between patient space and image space.

The patient 80 can also be tracked as the patient moves with an opticaltracker 88. Alternatively, or in addition thereto, the patient 30 may befixed within navigation space defined by the navigation system 26 toallow for registration. As discussed further herein, registration of theimage space to the patient space or subject space allows for navigationof the instrument 68 with the image data. When navigating the instrument68, a position of the instrument 68 can be illustrated relative to imagedata acquired of the patient 30 on a display device 84. Various trackingsystems, such as one including an optical localizer 88 or anelectromagnetic (EM) localizer 94 can be used to track the instrument68.

More than one tracking system can be used to track the instrument 68 inthe navigation system 26. According to various embodiments, these caninclude an electromagnetic tracking (EM) system having the EM localizer94 and/or an optical tracking system having the optical localizer 88.Either or both of the tracking systems can be used to track selectedtracking devices, as discussed herein. It will be understood, unlessdiscussed otherwise, that a tracking device can be a portion trackablewith a selected tracking system. A tracking device need not refer to theentire member or structure to which the tracking device is affixed orassociated.

It is further appreciated that the imaging device 80 may be an imagingdevice other than the O-arm® imaging device and may include in additionor alternatively a fluoroscopic C-arm. Other exemplary imaging devicesmay include fluoroscopes such as bi-plane fluoroscopic systems, ceilingmounted fluoroscopic systems, cath-lab fluoroscopic systems, fixed C-armfluoroscopic systems, isocentric C-arm fluoroscopic systems, 3Dfluoroscopic systems, etc. Other appropriate imaging devices can alsoinclude MRI, CT, ultrasound, etc.

In various embodiments, an imaging device controller 96 may control theimaging device 80 and can receive the image data generated at the imagecapturing portion and store the images for later use. The controller 96can also control the rotation of the image capturing portion of theimaging device 80. It will be understood that the controller 96 need notbe integral with the gantry housing 82, but may be separate therefrom.For example, the controller may be a portions of the navigation system26 that may include a processing and/or control system including aprocessing unit or processing system 102. The controller 96, however,may be integral with the gantry housing 82 and may include a second andseparate processor, such as that in a portable computer.

The patient 30 can be fixed onto an operating table 104. According toone example, the table 104 can be an Axis Jackson® operating table soldby OSI, a subsidiary of Mizuho Ikakogyo Co., Ltd., having a place ofbusiness in Tokyo, Japan or Mizuho Orthopedic Systems, Inc. having aplace of business in California, USA. Patient positioning devices can beused with the table, and include a Mayfield® clamp or those set forth incommonly assigned U.S. patent application Ser. No. 10/405,068 entitled“An Integrated Electromagnetic Navigation And Patient PositioningDevice”, filed Apr. 1, 2003 which is hereby incorporated by reference.

The position of the patient 30 relative to the imaging device 80 can bedetermined by the navigation system 26. The tracking device 62 can beused to track and locate at least a portion of the imaging device 80,for example the gantry housing 82. The patient 30 can be tracked with anon-invasive dynamic reference frame 170, as discussed further herein.That is, a patient tracking device 170 may be used to receive orgenerate electromagnetic signals that are communicated through a cable172 to an interface portion 110. As is discussed below wirelesscommunication to the interface portion 110 may also be used. The patienttracking device 170 may also be referred to as a dynamic referenceframe. The patient tracking device 170 is located within a substantiallyrigid body cavity. In the following example, the body cavity is a nasalcavity or palate as will be described in more detail below. A piece oftape 174 may be used to secure the cable 172 to the patient 30.

Accordingly, the position of the patient 30 relative to the imagingdevice 80 can be determined. Further, the location of the imagingportion can be determined relative to the housing 82 due to its preciseposition on the rail within the housing 82, substantially inflexiblerotor, etc. The imaging device 80 can include an accuracy of within 10microns, for example, if the imaging device 80 is an O-Arm® imagingdevice sold by Medtronic Navigation, Inc. having a place of business inLouisville, Colo. Precise positioning of the imaging portion is furtherdescribed in U.S. Pat. Nos. 7,188,998; 7,108,421; 7,106,825; 7,001,045;and 6,940,941; all of which are incorporated herein by reference,

According to various embodiments, the imaging device 80 can generateand/or emit x-rays from the x-ray source that propagate through thepatient 30 and are received by the x-ray imaging receiving portion. Theimage capturing portion generates image data representing theintensities of the received x-rays. Typically, the image capturingportion can include an image intensifier that first converts the x-raysto visible light and a camera (e.g. a charge couple device) thatconverts the visible light into digital image data. The image capturingportion may also be a digital device that converts x-rays directly todigital image data for forming images, thus potentially avoidingdistortion introduced by first converting to visible light.

Two dimensional and/or three dimensional fluoroscopic image data thatmay be taken by the imaging device 80 can be captured and stored in theimaging device controller 96. Multiple image data taken by the imagingdevice 80 may also be captured and assembled to provide a larger view orimage of a whole region of a patient 30, as opposed to being directed toonly a portion of a region of the patient 30. For example, multipleimage data of the patient's 30 spine may be appended together to providea full view or complete set of image data of the spine.

The image data can then be forwarded from the image device controller 96to the navigation computer and/or processor system 102 that can be apart of a controller or work station 98 having the display 84 and a userinterface 106. It will also be understood that the image data is notnecessarily first retained in the controller 96, but may also bedirectly transmitted to the work station 98. The work station 98 canprovide facilities for displaying the image data as an image 108 on thedisplay 84, saving, digitally manipulating, or printing a hard copyimage of the received image data. The user interface 106, which may be akeyboard, mouse, touch pen, touch screen or other suitable device,allows the user 72 to provide inputs to control the imaging device 80,via the image device controller 96, or adjust the display settings ofthe display 84. The work station 98 may also direct the image devicecontroller 96 to adjust the image capturing portion of the imagingdevice 80 to obtain various two-dimensional images along differentplanes in order to generate representative two-dimensional andthree-dimensional image data.

With continuing reference to FIG. 1, the navigation system 26 canfurther include the tracking system including either or both of theelectromagnetic (EM) localizer 94 and/or the optical localizer 88. Thetracking systems may include a controller and interface portion 110. Theinterface portion 110 can be connected to the processor system 102,which can include a processor included within a computer. The EMtracking system may include the STEALTHSTATION® AXIEM™ NavigationSystem, sold by Medtronic Navigation, Inc. having a place of business inLouisville, Colo.; or can be the EM tracking system described in U.S.Pat. No. 7,751,865 issued Jul. 6, 2010, and entitled “METHOD ANDAPPARATUS FOR SURGICAL NAVIGATION”; U.S. Pat. No. 5,913,820, entitled“Position Location System,” issued Jun. 22, 1999; and U.S. Pat. No.5,592,939, entitled “Method and System for Navigating a Catheter Probe,”issued Jan. 14, 1997; all of which are herein incorporated by reference.It will be understood that the navigation system 26 may also be orinclude any appropriate tracking system, including a STEALTHSTATION®TREON® or S7™ tracking systems having an optical localizer, that may beused as the optical localizer 88, and sold by Medtronic Navigation, Inc.of Louisville, Colo. Other tracking systems include an acoustic,radiation, radar, etc. The tracking systems can be used according togenerally known or described techniques in the above incorporatedreferences. Details will not be included herein except when to clarifyselected operation of the subject disclosure.

Wired or physical connections can interconnect the tracking systems,imaging device 80, etc. Alternatively, various portions, such as theinstrument 68 may employ a wireless communications channel, such as thatdisclosed in U.S. Pat. No. 6,474,341, entitled “Surgical CommunicationPower System,” issued Nov. 5, 2002, herein incorporated by reference, asopposed to being coupled directly to the processor system 102. Also, thetracking devices 62, 66, 170 can generate a field and/or signal that issensed by the localizer(s) 88, 94.

Various portions of the navigation system 26, such as the instrument 68,and others as will be described in detail below, can be equipped with atleast one, and generally multiple, of the tracking devices 66. Theinstrument can also include more than one type or modality of trackingdevice 66, such as an EM tracking device and/or an optical trackingdevice. The instrument 68 can include a graspable or manipulable portionat a proximal end and the tracking devices may be fixed near themanipulable portion of the instrument 68.

Additional representative or alternative localization and trackingsystem is set forth in U.S. Pat. No. 5,983,126, entitled “CatheterLocation System and Method,” issued Nov. 9, 1999, which is herebyincorporated by reference. The navigation system 26 may be a hybridsystem that includes components from various tracking systems.

According to various embodiments, the navigation system 26 can be usedto track the instrument 68 relative to the patient 30. The instrument 68can be tracked with the tracking system, as discussed above. Image dataof the patient 30, or an appropriate subject, can be used to assist theuser 72 in guiding the instrument 68. The image data, however, isregistered to the patient 30. The image data defines an image space thatis registered to the patient space defined by the patient 30. Theregistration can be performed as discussed herein, automatically,manually, or combinations thereof.

Generally, registration allows a translation map to be generated of thephysical location of the instrument 68 relative to the image space ofthe image data. The translation map allows the tracked position of theinstrument 68 to be displayed on the display device 84 relative to theimage data 108. A graphical representation 68 i, also referred to as anicon, can be used to illustrate the location of the instrument 68relative to the image data 108.

Referring now to FIGS. 2 and 3A, the endonasal tracking device orpatient tracking device 170 and cable 172 are illustrated disposedwithin a sensor housing 310 within a body cavity 312 of a patient 30.The patient tracking device 170 may be used as a dynamic reference frame(DRF) for various procedures such as but no limited to cranialprocedures. The housing 310 may be formed of a conformable material suchas a nasal tamponade (e.g. Merocel® nasal dressing by Medtronic). Thecavity 312 may be a cranial cavity such as a nasal cavity having anirregular shape. The housing 310 may be conformable to the shape of thecavity 312. The housing 310 may transform its shape to be secured withinthe cavity 312 automatically or automatically in the presence ofmoisture such as water or bodily fluids. As will be described in moredetail below, the size of the housing 310 may vary depending upon theparticular body cavity 312 into which the patient tracking device 170 islocated.

In FIGS. 2 and 3A-3C, the body cavity 312, in this example, is a nasalcavity such as the inferior nasal meatus. The body cavity 312 may berigid. Other nasal cavities such as the middle and superior meatus mayalso receive a sensor housing 310 with appropriate changes todimensions. Of course, the disclosure should not be limited to cranial,nasal cavities, oral cavities or surgical procedures. The sensor housing310 is substantially, non-invasively fixed relative to the patient 30and particularly fixed relative to the skull or cranium. A nasalspeculum 180 may be used to insert the housing 310 and sensor 320 withinthe cavity 312. The housing 310 may be compressed during insertion. Thehousing 310 may expand into and conform to the cavity 312. The housing310 may also be removed by way of a tool such as the nasal speculum. Thehousing 310 may have a first form at rest, a second form as it is beinginserted and a third form within the body cavity.

The cable 172 is coupled to an electromagnetic sensor 320 that eithergenerates an electromagnetic field or receives electromagnetic fieldfrom the EM localizer 94 and generates a current in the presence of theelectromagnetic field. The cable 172 communicates signals to or from thesensor 320 depending on the mode of operation mentioned previously. Thesignals from the sensor 320 allow precise position of the sensor 320 tobe determined relative to the components within the operatingenvironment. One example of a suitable sensor 320 is an AxiEM sensor.

The housing 310 may optionally have a removing member or handle 326coupled thereto. The handle 326 may be one or more strings or otherflexible device that is used for removing the housing 310 from thesubject 30. The handles 326 are particularly useful if the patienttracking device 170 is wireless.

Referring now to FIG. 3B, a different shape of housing 310 is set forth.In this example the housing 310 is shorter in length and has a dimensionto fit within the entry to the nasal passage.

Referring now to FIG. 3C, a larger housing 310 is illustrated having thesensor 320 disposed therein. In this example, the housing 310 is thickerand longer than those set forth in FIGS. 3A and 3B. As mentioned above,the shape of the housing 310 may vary depending upon the particular bodycavity 312 as well as the size of the body cavity 312 and the size ofthe patient.

The housing 310 may automatically take the shape of the body cavity tosubstantially fix the sensor 320 in relation to the subject 30 in anon-invasive manner. The housing 310 may conform to an opening such as anasal passage as it is being inserted. The sensor is fixed in shape andsmall enough to enter the desired opening. The housing 310 conforms tothe cavity shape without the cavity having to conform to the housing. Inthis manner the housing 310 and sensor 320 are held in place during aprocedure. The housing is non-invasively fixed to the subject.

Referring now to FIGS. 4A and 4B, a detailed view of one example of apatient tracking device 170 is set forth. In this example a connector410 is used for connecting the patient tracking device 170 to theinterface 110 set forth above. In FIG. 4A, the housing 310 isillustrated disassembled from the sensor 320. In FIG. 4B, the sensor 320is illustrated within the housing 310. Details of the assembly of thehousing 310 and the sensor 320 are set forth in greater detail below.

Referring now to FIG. 5, an exemplary electromagnetic EM coilconfiguration for the sensor is illustrated. An electromagnetic sensorbobbin 510 or multiple coil members may be positioned in a cavity of thepatient tracking device 170. The sensor bobbin 510 includes a body 512that is generally formed from material that is not conductive to allowthe coils to operate and sense a position in a field. In addition, thebody 512 may be manipulated by a manipulable portion or handle 514extending from the body 512. In addition, the handle 514 may allow cable172 to be interconnected to the body portion 512 into multiple coils. Inthis example, three coils 516, 518 and 520 are illustrated. However,fewer coils or more coils may be used in a sensor.

The first coil 516, the second coil 518 and third coil 520 are generallypositioned at angles relative to one another. The angles may be anyappropriate angle such as a generally orthogonal angle or otherappropriate angle. The three coils 516, 518, 520 being positioned atangles relative to one another, allow for six degrees of freedom sensingincluding translation, angle, pitch, yaw, and rotation. Therefore, theposition or movement of the patient tracking device 170 can bedetermined by sensing the electromagnetic field of the electromagneticlocalizer 138.

Generally, the body 512 of the bobbin 510 and the exterior or the bodiesof the patient tracking device 170 are formed of an appropriatematerial. For example, the material may be a non-metallic andnon-conducting material such as an appropriate ceramic, plastic, and thelike. The material may be selected from a material that will notinterfere with either transmitting or receiving information regardingthe magnetic field and not interfere with imaging of the subject 30.

Referring now to FIG. 6A, the housing 310 is illustrated in furtherdetail. The housing 310 may be formed of a flexible, resilient andconformable material such as nasal dressing (e.g. a nasal tamponade).The housing 410 is autoconformable and resilient in that the shape ofthe housing 410 automatically conforms to the shape of the cavity wheninserted therein. In one example, the material is compressible andexpandable when in contact with a fluid such as water. In either case,the housing material automatically fills and conforms to the cavityshape. The housing 310 is illustrated in its expanded form. The materialof the housing 310 may also be sterile and disposable. In one example,the housing 310 is formed of hydroxylated polyvinyl acetate which is acompressed foam polymer. The material is conformable and compliant sothat when the housing 310 is placed within a body cavity, theirregularities of the body cavity 312 are compensated for by theconforming housing 310. That is, the housing 310 may be retained in afixed position within the body cavity 312 due to the conformable andcompliant nature. The housing 310 is also resilient in that it may becompressed before or during placement within the body cavity 312 andexpands after positioning within the body cavity 312 from a firstconfiguration to a second configuration. As mentioned above, thematerial forming the housing 310 may be expandable when in contact withmoisture or water. The housing 310 may include a longitudinallyextending slot 610. In the present example the slot 610 is about halfway between the thickness T and extends a length L less than the lengthof the housing 310.

Referring now to FIG. 6B, the slot 610 is illustrated in a lateral endside 612. The slot 610 extends a width W less than the width of thehousing 310. The width W of the slot 610 is sized to receive the sensor320 and cable 172 therein.

Referring now to FIG. 6C, the interior of the housing 310 may bepre-formed with a cavity 614 for receiving the sensor 320 therein. Thecavity 614 may also be formed by placing the sensor 320 into the slot610 within the housing 310. That is, because the material of the housing310 is compressible, when the sensor 320 is inserted within the slot610, the cavity 614 may be formed. The material directly adjacent to thecavity 614 may be more highly compressed than the material further fromthe cavity 614.

In a set of patient tracking devices, the length, width and thickness ofmultiple devices may vary to allow a number of options depending on thepatient and cavity characteristics.

A retainer may optionally be used to secure the sensor within the cavity614. In this example, the retainer may be an adhesive 616 that isdisposed on at least some of the surfaces of the cavity 614. In thismanner, when the sensor 320 is disposed within the cavity 614, thesensor 320 remains engaged with the housing 310. In one example, a dropor two of an adhesive material may be communicated through the slot 610in to the cavity 614 prior to the insertion of the sensor 320 within thecavity 614. Ultimately, the adhesive 616 is forced toward the surfacesof the cavity 614. The types of retainers may be flexible andconformable to allow the patient tracker to conform to the cavity.

Referring now to FIG. 6D, the sensor 320 may not completely fill thecavity 614. A biocompatible material 620 may be injected into theunfilled portion of the cavity 614 to securely lodge the electromagneticsensor 320 and the cable 172 therein. A suitable biocompatible materialis polylactic acid.

Referring now to FIG. 7A, the electromagnetic sensor 320 is illustratedwith a cable 172 thereon. Adhesive 710 may be applied to the outersurface of the sensor 320 so that upon insertion within the cavity 614of FIG. 6B the sensor is maintained therein.

Referring now to FIG. 7B, a wireless electromagnetic sensor 320′ mayalso be provided. In this example, the wireless EM sensor may be formedwith sensing coils 720 as described above. However, a wirelesscommunication may be formed with the interface using a transmitter 722.Thus, the wireless EM sensor 320′ may be fully enclosed within thehousing 310 and thus no wire or cable 172, such as that illustratedabove, is required for communication with the interface 110.

Referring now to FIG. 8A, one example of an assembled patient trackingdevice 170 is set forth. The handles 326 which are optional in all ofthe figures, are illustrated. The handles 326 may be drawstrings thatare embedded within the material of the housing 310. The handles 326 maybe adhesively bonded within the housing 310 so that they may be used toremove the patient tracking device 170 when the patient tracking deviceis no longer needed. In this example, the sensor 320 is held within thehousing 310 by adhesive 810 disposed at the interface between the sensorhousing 310 and cable 172.

Referring now to FIG. 8B, the same reference numerals are used as thoseset forth in FIG. 8A. However, in this example a clip or fastener 820 isused for securing the cable 172 to the housing and thus the sensor 320is secured within the cavity of the housing 310.

Referring now to FIG. 170, another type of clip or fastener 822 isillustrated. In this example the clip or fastener 822 extends from anupper surface 824 to a lower surface 826. The clip or fastener 822 hasarms 828 that are directly adjacent to the respective surfaces 824 and826 and provide a clamping force to secure the cable 172 therein. Asmentioned above, the clips or fasteners may be flexible so that theyallow the housing to be inserted into the body cavity.

In FIGS. 8A and 8B, the clips or fasteners 820, 822 may be formed of adielectric material so that they do not interfere with theelectromagnetic fields sensed or generated by the electromagnetic sensor320.

The sensor 320 may also be secured by heat sealing or by overmolding thesensor 320 within the material of the housing 310 during the forming ofthe housing 310. The handles 326 may also form a drawstring that areused to secure the cable 172 to the housing or close the slot so thatthe sensor 320 is retained within the housing 310.

The handles 326 may not be required should the housing 310 be removedwith a separate instrument. The housing 310 may also be removed bypulling on the cable 172. In such a case, the retainer such as theadhesive 810, or the clips or fasteners 820, 822 are stronger than theforce required to pull the housing 310 from the body cavity of thesubject 30.

Referring now to FIG. 9A, the wireless EM sensor 320′ is illustrated infurther detail. In this example, the handles 326 may be required toallow removal of the housing 310 from the body cavity of the subject. InFIGS. 9A-9C the slot 610 illustrated above in FIGS. 6A-6B areillustrated. In FIGS. 8A-8C the slot has been filled by the cable 172.However, in the case of the RF EM sensor 320′ no wire is required. Thus,when the sensor 320′ is inserted within the cavity 614, the slot 610 maybe sealed with adhesive 910. FIGS. 9B and 9C may use clips or fasteners820, 822 to enclose the sensor 320′ within the cavity of the housing310.

Referring now to FIG. 10, a method for forming the patient trackingdevice 170 is set forth. In block 1010, a cavity is formed within thehousing. As mentioned above, the housing may be conformable and thecavity may be pre-formed or automatically formed as the sensor 320 isinserted within the housing 310. In block 1012, the sensor 320 ispositioned within the cavity 614. The sensor may be positioned withinthe cavity 614 by insertion through the slot 610 illustrated above. Inblock 1014, the sensor is secured within the housing using a retainersuch as but not limited to adhesive, clips, fasteners, overmolding, orheat staking, et cetera.

Referring now to FIG. 11, the use of the patient tracking device for aprocedure is set forth. In block 1110, the subject is imaged. During theimaging of the subject, the body cavity within which the patienttracking device is to be secured during the procedure may be determined.In block 1112, the cavity size is determined for the body cavity basedupon the image determined in block 1110.

An optional block 1114 may also be performed. In block 1114, the patienttracking device may be coupled to an instrument such as a nasal speculumfor insertion. However, an instrument such as a nasal speculum may notbe required if the patient tracking device is in a compressed statebefore insertion. The use and type of the instrument in block 1114depends upon the particular body cavity and the type of sensor and thematerial of the housing.

In block 1116, the sensor housing may be compressed manually or using aninstrument. This is an optional block since the sensor housing may alsobe compressed prior to insertion or during insertion by the rigid bodycavity walls. In block 1118 the patient tracking device is inserted intothe body cavity. In block 1120, the patient tracking device housing isautomatically expanded to conform, nest, deform or otherwise be fixedinto to the body cavity. That is, the housing 310 is changed from afirst configuration or shape into a second configuration or shape. Inblock 1122, the cable is secured to the patient using an adhesive ortape. In block 1124, the procedure is performed. During the procedure,block 1126 collects data from the patient position sensor (DRF) andadjusts the navigation location in block 1128. The navigation locationin block 1128 maintains the registration of the patient and the image inresponse to any movement of the patient. The correlation of the patientand the images is maintained.

In block 1130, the patient tracking device may be removed from thepatient and disposed of. The conforming housing may allow the patienttracking device to easily be removed by handle, cable or using aninstrument. In this manner, the insertion and the removal of the patienttracking device is non-invasive to the subject.

The sensor assembly set forth herein may be used as a dynamic referenceframe and is particularly suited for body cavity insertion such as anasal cavity during cranial procedures. The housing 310 may becompressed manually or by tool (or not at all). The housing materialconforms to the rigid body cavity without deformation of the bodycavity. The sensor assembly can be used interopertively withoutincisions or fixing to the subject with screws or other invasivemethods.

Referring now to FIGS. 12 and 13, a sensor housing 1310 having anelectromagnetic sensor 320 coupled thereto may be mounted within an oralcavity 1320 of patient 30. The housing 1310 may be formed in variousways including three-dimensional printing. One suitable biocompatiblematerial for housing 1310 is polylactic acid. The housing 310 may beaffixed to the palate 1330 or teeth 1332 or both. The sensor housing1310 and electromagnetic sensor 320 may be used in the system of claim1. The use of the oral sensor housing 1310 is suitable for cranialprocedures when access to or through the nasal passages are required.

Referring now to FIGS. 14 and 15, the sensor housing 1310 is illustratedin further detail. The sensor housing 1310 includes a first surface 1410and a second surface 1412. The first surface 1410 is based upon thesurface of the palate 1330. As will be further described below, acomputed tomography (CT) image may be formed of the oral cavity of thepatient 30. The housing 1310 may be formed by three-dimensional printingor the like and may be based on the CT image in order for the firstsurface to rest with the palate. The housing may also be molded from anegative of the palate surface as is described below. The second surface1412 may be of an arbitrary shape and include a planer portion as willbe illustrated below. A third and fourth surface 1414 may be shaped toconform to the profile of the teeth so that ultimately an adhesive maybe used on the surfaces 1414 to adhesively join the teeth and thehousing 1310.

The surface 1410 may be formed especially for an individual patient.Also, the surface 1410 may be formed by a general patient size to berelatively close to various types of patients. That is, a set of varioussize housings 1310 may be formed for a doctor to select from. Thematerial of the housing may be flexible to allow a fit within the oralcavity. For example, a large, medium or small adult and a large, mediumor small child may all be sized differently. The surface 1410 may berounded generally to conform to the size. The surfaces 1414 may be usedto adhesively join one of the selected housings from the set of housingsto the patient 30.

Referring now to FIG. 16, a plurality of teeth 1332 are illustrated. Theteeth 1332 may be adhesively coupled to the sensor housing 1310 by anadhesive 1610. In addition to an adhesive on the teeth 1332, adhesive1610 on the palate or merely saliva from the patient may be used tosecure the sensor housing 1310 within the oral cavity 1320 of thepatient 30.

Referring now to FIG. 17, a side view of an assembled sensor housing1310 is set forth. The sensor housing 1310 is set forth in great detailin FIGS. 4A, 4B and 5. In all instances the electromagnetic sensor 320may be replaced with the wireless electromagnetic sensor 320′illustrated in FIG. 7B. The sensor 320 illustrated in FIG. 17, issecured to the surface 1412 with adhesive 1710.

Referring now to FIG. 18, the sensor 310 may be coupled to a planersurface 1810 of the sensor housing 1310′. In this example, the shape ofthe housing 1310′ is a convex shape and the sensor 310 is coupled to theplaner surface 1810. For this example, adhesive may also be used toaffix the housing 1310′ to the teeth 1332.

Referring now to FIG. 19, the sensor 310 may also be formed within acavity 1910 of the sensor housing 1310″. The cavity 1910 may be sized toreceive the sensor 310 therein as well as allowing the wire 172 toextend therefrom. A biocompatible material 1912 may be used to retainthe electromagnetic sensor 310 within the cavity 1910. The biocompatiblematerial 1912 may be an adhesive or may be formed from the same materialas the housing 1310″.

Referring now FIG. 20, the electromagnetic sensor 310 may be over-moldedwithin the material of the housing 1310′″. The first surface 1410 andthe second surface 1412 may be formed in a similar manner.

Referring now to FIG. 21, a method for forming the palate housing is setforth. In step 2110 a shape of the patient's palate is determined. Theshape of the patient's palate may be formed by a noninvasive method suchas using a CT image. In step 2112, the CT image may be used to form thesensor housing and in particular the first surface of the sensor housingto correspond to the shape of the palate. An exact mirror image of thepalate surface of the patient may be obtained using the CT image.However, a completely exact match is not necessary. The sensor housingmay be three-dimensionally printed based on the CT scan. Alternatively,a negative print of the palate may be obtained. The sensor housing mayuse the negative print as a surface of a mold. That is the housing ismolded based on the negative print. The sensor housing may then beadhesively coupled to the sensor using adhesive heat staking or thelike. As mentioned above, over-molding the sensor may also beover-molded within the material of the sensor. The sensor may be affixedwithin the oral cavity to perform a procedure as described above.

In all cases, the material of the sensor housing may have a slight flexso that, when inserted into the palate of a patient the housing flexesand provides force against the teeth, the palate or both for retainingor helping retain the housing within the oral cavity. For example, inFIG. 18 arrows 1820 represent inward flexing for insertion and arrows1830 illustrate the direction of flex after release into the patient.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention. Individual elements or features ofa particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the invention, and all such modificationsare intended to be included within the scope of the invention.

It should be understood that various aspects disclosed herein may becombined in different combinations than the combinations specificallypresented in the description and accompanying drawings. It should alsobe understood that, depending on the example, certain acts or events ofany of the processes or methods described herein may be performed in adifferent sequence, may be added, merged, or left out altogether (e.g.,all described acts or events may not be necessary to carry out thetechniques). In addition, while certain aspects of this disclosure aredescribed as being performed by a single module or unit for purposes ofclarity, it should be understood that the techniques of this disclosuremay be performed by a combination of units or modules associated with,for example, a medical device.

In one or more examples, the described techniques may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored as one or more instructions orcode on a computer-readable medium and executed by a hardware-basedprocessing unit. Computer-readable media may include non-transitorycomputer-readable media, which corresponds to a tangible medium such asdata storage media (e.g., RAM, ROM, EEPROM, flash memory, or any othermedium that can be used to store desired program code in the form ofinstructions or data structures and that can be accessed by a computer).

Instructions may be executed by one or more processors, such as one ormore digital signal processors (DSPs), general purpose microprocessors,application specific integrated circuits (ASICs), field programmablelogic arrays (FPGAs), or other equivalent integrated or discrete logiccircuitry. Accordingly, the term “processor” as used herein may refer toany of the foregoing structure or any other physical structure suitablefor implementation of the described techniques. Also, the techniquescould be fully implemented in one or more circuits or logic elements.

What is claimed is:
 1. A patient tracking device for insertion into abody cavity comprising: a flexible conformable sensor housing comprisinga sensor cavity therein, wherein the housing conforms to the body cavitywhen inserted therein; and a sensor disposed within the housing.
 2. Thepatient tracking device as recited in claim 1 further comprising ahandle coupled to the housing for removing the housing from the bodycavity.
 3. The patient tracking device as recited in claim 2 wherein thehandle comprises a string coupled to the sensor housing.
 4. The patienttracking device as recited in claim 1 wherein the sensor comprises anelectromagnetic sensor with a wired communication cable for wiredcoupling to an interface.
 5. The patient tracking device as recited inclaim 4 wherein said wired communication cable extends through a lateralend side of the sensor housing.
 6. The patient tracking device asrecited in claim 5 wherein the lateral end side comprises a slot coupledto a cavity, said slot and cavity sized to receive said sensor.
 7. Thepatient tracking device as recited in claim 1 further comprising asensor retainer retaining the sensor within the sensor cavity.
 8. Thepatient tracking device as recited in claim 7 wherein the sensorcomprise an electromagnetic sensor with a wireless transmitter forwirelessly communicating with an interface.
 9. The patient trackingdevice as recited in claim 7 wherein the sensor retainer comprises afastener, clip, or adhesive.
 10. The patient tracking device as recitedin claim 7 wherein the sensor retainer comprises a draw string.
 11. Thepatient tracking device as recited in claim 7 wherein the sensorretainer is housing material overmolded around the sensor.
 12. Thepatient tracking device as recited in claim 7 wherein the sensorretainer comprises a heat seal.
 13. The patient tracking device asrecited in claim 1 wherein the housing is composed of hydroxylatedpolyvinyl acetate.
 14. A method comprising: determining a body cavityfor receiving a flexible resilient sensor housing; determining a sensorhousing corresponding the body cavity; inserting the sensor housinghaving a sensor within a sensor cavity of the housing into the bodycavity; conforming the sensor housing to a shape of the body cavity;collecting position data of the body cavity from the sensor; maintainingregistration of an image space to a patient space in response to theposition data; and displaying a navigated location.
 15. The method asrecited in claim 14 wherein inserting comprises inserting the sensorhousing using a speculum.
 16. The method as recited in claim 14 furthercomprising removing the sensor from the body cavity using a handleextending out of the body cavity.
 17. The method as recited in claim 14further comprising inserting the sensor within the cavity of the sensorhousing prior to inserting the sensor into the body cavity.
 18. Themethod as recited in claim 17 further comprising retaining the sensor inthe cavity using the sensor housing.
 19. The method as recited in claim14 wherein conforming comprises expanding the sensor housing within thebody cavity.
 20. The method as recited in claim 14 wherein insertingcomprises inserting the sensor housing into a sinus cavity.
 21. Themethod as recited in claim 14 wherein collecting position data comprisesnavigating a cranial procedure.
 22. The method as recited in claim 14wherein conforming the sensor comprises conforming the sensor housingfrom a first form to a second form during insertion and conforming thesensor housing to a third form during maintaining registration.
 23. Amethod of forming a patient tracking device comprising: forming a sensorcavity within a flexible conformable housing sized to fit within a bodycavity; inserting an electromagnetic sensor within the sensor cavity;and retaining the electromagnetic sensor within the sensor cavity. 24.The method as recited in claim 23 wherein retaining the electromagneticsensor comprises retaining the electromagnetic sensor by using at leastone of a fastener, clip, adhesive, drawstring, overmolding and a heatseal.